Signaling system



July 18, 1939. J. l.. FlNcl-l SIGNALING SYSTEM Filed Feb. 4, 1958 mg Noix INVENTOR L F//V H BY )fg Al'TORNEY ww uw Lax N am.

wmqu NQSQ NGN vw NMS Patented July is, 1939 UNITED STATES SIGNALING SYSTEDI James Finch, Patchogue, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application February 4, 1938, Serial No. 188,700

This application concerns a new and improved signaling system adapted for producing wave energy, amplifying and keying the same and transmitting the same. The invention is also appli- '5 cable to the production of wave energy, phase modulation of the wave energy, amplification and keying of the phase modulated wave energy and transmission of the same. A feature of the invention is the use of a non-linear resistance l shunting the keying tube to protect the same from destruction in the case 'of failure of the circuits or improper operation thereof in any respect, which results in excessive voltages being placed on the keying tube.

In describing my invention in detail reference will be made to the drawing wherein the single figure illustrates the mai'n features of my invention.

In the drawing, wave energy for signaling purposes is produced by an oscillator comprising an electron discharge -device l0 having its electrodes connected in oscillation producing circuits including a piezo-electric crystal l2. The tube I0 is preferably of the screen grid type so that 2;, undesired coupling is prevented and, as will be noted, this oscillator relies solely on the crystal fortuning the same to the desired frequency.

Obviously, this results in oscillations of substantially constant frequency being developed at all 3., times. The. oscillations produced in Ill are suppliedto an amplifier tube I 6 which has its control grid IB coupled to the anode of I0. The

amplifier I8 may simultaneously multiply the frequency of the produced oscillations and its u output circuit may be tuned to the fundamental or a harmonic of the fundamental to which the wave energy is to be multiplied'.

Wave energy is-supplied from the output circuit of amplier i6 to an additional amplifier 20 4 having its control grid 22 coupled to the anode circuit of I6. The amplifier 20 may also multiply the frequency of the waves supplied thereto, in

,which case its anode circuit may be tunedto the frequency, supplied from the output of i6 or 4,-, to a multiple thereof. The tuned circuit 30 is connected `between` the anode 2l and a point 'of high potential on a source of potential not shown. 'Ihis amplifier 2B `also serves as the keyed stage, as will be described hereinafter. A third amplifier 50 comprising an electron discharge device 26, has its control 4grid 28 coupled to the tuned circuit 30 to derive therefrom voltages of the frequency to which Y30 is tuned. These voltages are amplified in 2B, appear in' tuned circuit 32, and are 55 impressed on the input of an additionalpush-pull amplifier comprising tubes 34 and 36. The output electrodes of tubes 34 and 36 are connected by a tuned tank circuit 3B which supplies the amplified wave energy to an additional and final amplifier comprising tubes 40 and 42. The output of tubes 40 and 42 appears in the tuned circuit 44 and is supplied therefrom to a coupled inductance 46 and from 46 to any utilization circuit.

The electrode energizing circuits are, to some extent, conventional and are not of the present invention except as otherwise described in detail below.

In order to regulate voltages, non-linear resistances, such as Thyrite, are used in the ener# gizing circuits, as for example, in the cathode return of the tubes 40 and 42 and in shunt to the source of potential not shown. 'I'he drop of potential through theseAnon-linear resistances does not increase as rapidly as change of current therethrough increases and therefore more constant voltages are available for the electrodes in the tubes of the circuits.

'I'he oscillator l0, if desired, may' be phase modulated by signals applied to a transformer 50, the secondary of which is between the cathode 52 of oscillator l0 and point of low potential. This cathode is swung relative to ground in accordance with the potentials applied at and the oscillations produced in i0 are thereby phase modulated due to the changes in the cathode to grid current, impedances, reactance, etc. The manner in which this phase modulation is accomplished has been set forth more in detail in Goldstine United States Patents #2,067,081, dated January 5, 1937; #2,067,082, dated January 5, 1937, and Patent 2,111,587, dated March 22, 1938. If the potentials applied at 50 are intelligible signals the oscillations produced in l0 are modulated in accordance with said signals. When telegraphy signals are to be transmitted in this particular embodiment the signals at 50 may be of a single frequency so that the generated oscillations in I0 are wobbled in phase around a point of substantially fixed phase. 'I'his wobbling of the phase orA frequency of the produced oscillations enhances the transmission effectiveness thereof by obtaining the benefits of frequency diversity in transmission.

The oscillations generated in I0, Wobbled in phase, as described above or unmodified by waves at 50 are keyed by a keying system of the absorber type comprising a tube 60 having its grid 62 coupled to any source of keying potentials as shown and its anode 64 connected with the anode 2l of amplifier tube 2l through the inductance of tuned circuit Il. By this connection the current and voltage supplied by the line il is shared by tubes Il and ll. When l2 is biased more positive or less negative relative to the cathode II of tube Il the tube draws more current to thereby rob tube Il of current and voltages land the wave amplitude supplied by Il to 2l is reduced. When the grid il of tube il is made more negative or less positive relative to the cathode 66,' tube l draws less current and tube 20 gets more voltage and current in its anodecircuit and the amplitude of the wave energy supplied from circuit 3l to tube 2l goes up. In this manner keying is accomplished. f

To obtain potentials intermediate between those of terminals I8 and 10 for various circuits of this transmitter a potentiometer is connected between Il and 10 and connections made along this potentiometer to obtain these voltages. During keying operations the current drawn from these connections varies widely and tends to cause. the potentials to depart from the desired values. 'I'his tendency is very greatly reduced by employing in the potentiometer non-linear resistances such as Thyrite so that the voltage drop grows at a rate less than linear relative to incease in current drawn. 'Ihis causes the voltage to bemore constant on all stages during operation and in particular on the oscillator stage, thereby improving stability of operation.

'I'he keying tube 6U has its anode to cathode impedance shunted by a non-linear resistance 80 such as Thyrite to prevent destruction of this tube in the event of failure of the equipment such as results for example, in over-loading Bil by excessive voltage from 8B and 10: Interruption of the plate circuit of tube is an example of failure or improper operation which might cause overload on 8l. Likewise, accidental removal of several of the stages would unload the source of direct current to an extent such that excessive voltages appear across the anode and cathode of il. The non-linear resistance 80 is of a value and impedance such that it shortcircuits excessive voltages and dissipates the energy of the current produced thereby to thereby protect tube Il.

The non-linear resistances referred to hereinbefore are of a nature such that the potential drop thereacross does not increase linearly with respect to current increase therethrough. That is, the resistance value of the material used decreases faster than linear with respect to voltage increases so that current therethrough increases at a rate greater than linear with respect to the voltage increases. A material of this nature having the trade name Thyrite has been described by K. B. McEachron in his Patent No. 1,822,742, dated September 8, 1931.

I claim:

1. In a signaling system, an electron discharge device having electrodes connected with a common source of potential, means for maintaining the voltages applied to said electrodes by said source of potential of substantial constant value comprising non-linear resistances shunting said source; means for varying the impedance of said discharge device at signal frequency and means for protecting said device against excessive voltages comprising anon-linear resistance shunting the electrodes of said device to dissipate excessive energy applied thereto.

2. In a telegraph system a keyed stage including an electron discharge device having electrodes aromas and a keying stag'e comprising an electron discharge device having electrodes connected with electrodes in said keyed stage and with a common source of potential, means for varying the impedance of said keying stage discharge device at signal frequency and a non-linear resistance shunting the electrodes of said keying stage device to bypass Aexcessive voltage applied thereto. 3. In a telegraph system, an electron discharge device having a plurality of electrodes, means for impressing wave' energy on one of said electrodes, a utilization circuit coupled with other of said electrodes, a source of direct current voltage, a keying tube having a controlling electrode connected with a source of keying potentials and having electrodes coupled in shunt to electrodes of said first named device and to said source of voltage whereby voltage supplied to the. electrodes of said first named device is controlled in accordance with the keying potentials on the controlling electrode of said second. named tube, and means for protecting said second named tube from excessive voltages comprising a non-linear resistance in shunt to a pair of electrodes thereof.

4. In a telegraph system, an electron discharge device having input electrodes and output electrodes, means for impressing phase wobbled oscillations on said input electrodes, a utilization circuit coupled with said output electrodes, a source of direct current voltage, a keying tube having a controllingelectrode connected with a source of keying potentials and output electrodes coupled in shunt to the output electrodes of said first named device and to said source of voltage whereby voltage supplied to said ilrst named device is controlled in accordance with the keying potentials on the input 'electrodes of said second named tube, and means for protecting said second named tube from excessive voltages comprlsing a non-linear resistance in shunt to-th output electrodes thereof. f

5. In a telegraph system, a source of oscillations of substantially constant frequency, an ame plifler tube having input electrodes coupled `with said source of oscillations and having output electrodes, additional amplifying tubes coupling said output electrodes of said iirst amplifying tube to a utilization circuit', a single source of direct current potential for supplying voltages to the output electrodes of all of said tubes, means for maintaining the voltages applied to said electrodes of substantially constant value comprising non-linear resistances shunting said source, a keying tube having input electrodes connected with a source of keying potentials and having output electrodes connected in shunt to the output electrodes of one of said amplifier tubes, and means for preventing excessive voltages from destroying said keying tube comprising a non-linear resistance in shunt to the output electrodes thereof.

6. In a telegraph system, a source of oscillations of substantially constant frequency, means for wobbling the phase. of said oscillations at tone frequency, an amplifier tube having input electrodes coupled with said source of oscillations and having output electrodes, additional amplifying tubes coupling said output electrodes of said first amplifying tube to a utilization circuit, a single source of direct current potential for supplying voltages to the output electrodes of all of said tubes, means for maintaining the voltages applied to said electrodes of substantially constant value comprising non-linear resistances shunting said source of 4direct current potential,

disease 3,.; a keying tube having irl-mult electrodes connected.'

with a source of keying potentials and having output electrodes connected -in shunt to the output electrodes of said ilrst named ampliiler tube.

and means for preventing excessive voltages from destroying said keying tube comprising a. nonlinear resistance in shunt to the output electrodes thereof.

'1. In a. telegraph system, an lelectron. discharge device havinge plurality of electrodes, means for impressing wave energy on electrodes Aof s aid device, a utilization circuit coupled with electrodes or said device, a source oi direct current potentiel. a keying tube having e wniwllle electro@ connected with a source of keying potentials und having electrodes .coupled toelectrodes o! said Afirst 'named device and to said source of potential whereby the impedance of said ilrst named device is controlled .in accordance with the keying potentials on the controlling electrode of said second named tube. and m for protecting said secondnsrned tube from excessive voltages, comprising ,a non-linear rance a pair of electrodes thereof. 

